# arithmetic progression question?

The perimeter of an octagon is 280 cm, the sides are in arithmetic progression

the longest side is 4 times the length of the shortest side find the length of the shortest side

correction, find the length of the longest side

### 2 Answers

- Ian HLv 71 month agoFavourite answer
Let the 8 sides in arithmetic progression be:-

a, a +d, a + 2d, .....a + 7d,

so that the longest side, a + 7d = 4a

Then the perimeter is the sum P = 8a + 28d = 280

Substituting 28d = 4(7d) = 12a

we get 20a = 280 and longest side, 4a = 56

Although not required, d = 6, and sides are

14, 20, 26, .......56

- Anonymous1 month ago
Sorry, my answer is "Anonymous" as your post is Anonymous. There is no need for an Anonymous question in this category, Most 'Anonymous' posts are trolls or people posting their homework, maybe yours is not, but the high likelihood is there. If you post as yourself, I would be glad to help you with any problem you have.

I spend a lot of time on each problem, I just want to make sure it's for a worthwhile cause.